Mitosis
• Deals exclusively with the division of the
cell nucleus.
• Creates identical daughter cells.
Interphase
• Period of time between splits.
• Most of cells growth takes place during
this time.
• Chromosomes are replicated (copied).
– There are now 2 copies of every
chromosome.
– Important: humans are diploid ( we have two
copies of each chromosome arranged in 23
pairs)
• Organelles are made.
4 phases of Mitosis
•
•
•
•
Prophase
Metaphase
Anaphase
Telophase
Prophase
• First and longest phase of mitosis.
– Chromatin condenses to form chromosomes
– Chromosomes become visible
– Centrioles separate and move to opposite ends of the
cell.
– Spindle fibers form
– Nuclear envelope and nucleolus begin to break down.
• Near the end of prophase the nuclear membrane
and nucleolus disappear.
Nuclear membrane
begins to dissolve
Centrioles move to opposite
ends
Gary E. Kaiser
By end of prophase
• Nucleolus has disappeared
• Spindle fibers span the cell
• Sister chromatids are attached to spindle
by centromere.
Metaphase
• Chromatids align down the center of the
cell. Each chromosome remains attached
to a spindle fiber at its centromere.
Anaphase
• Sister chromatids separate into individual
chromosomes and begin to be pulled to
opposite ends of the cell.
Telophase
• Chromosomes gather at opposite ends of
the cell and loose their distinctive shape.
• Nucleolus and nuclear membranes reform
• Spindle fibers dissolve.
• Essentially the reverse of prophase.
• Telophase overlaps with Cytokinesis
Cytokinesis
• Divides the cytoplasm of the cell.
• In animal cell, the cell membrane pinches
the cell in half creating two daughter cells
at the cleavage furrow.
• In plant cells, a cell plate forms between
the two nuclei, gradually develops into
separate membrane and then cell wall.
• Each cell has an identical set of duplicate
chromosomes.
Cleavage Furrow
Formation of 2 daughter cells